KR100601146B1 - Polyethylene resin composition for plastic closure and its article - Google Patents

Abstract

The present invention relates to a polyethylene resin composition for plastic bottle caps having low coefficient of friction properties, the alkyl silicone oxide compound is appropriately opened without causing a change in taste made by melt kneading polyethylene grafted on the polyethylene backbone with high density polyethylene. It relates to a polyethylene resin composition for a plastic bottle cap having a torque.

Description

Polyethylene resin composition for plastic bottle caps and molded articles manufactured therefrom {POLYETHYLENE RESIN COMPOSITION FOR PLASTIC CLOSURE AND ITS ARTICLE}

The present invention relates to a polyethylene resin composition for plastic bottle caps having a low coefficient of friction, wherein the alkyl silicon oxide compound is melt-kneaded and mixed with high-density polyethylene polyethylene grafted to the polyethylene main chain beverages such as water, carbonic acid, juice The present invention relates to a resin composition capable of opening a bottle cap with an appropriate force by reducing friction with a container such as a glass bottle and a polyethylene terephthalate mainly used as a container, and having excellent stability to taste, and a molded article manufactured therefrom.

Recently, due to the diversification of packaging containers and expansion of separate collection of environmental aspects, plasticization of bottle cap materials used for beverage containers such as glass bottles and polyethylene terephthalate is increasing. High-density polyethylene, polypropylene, etc. are mainly used as plastic bottle cap materials. Bottle caps based on these materials are lighter and less corrosive than conventional aluminum bottle caps. Its use is increasing due to the advantage that it can be molded.

In particular, high-density polyethylene is more flexible than polypropylene, so unlike the bottle cap of polypropylene material, which requires a separate liner to seal the contents of the beverage container, it can maintain the sealability of the contents without using a liner. It has advantages.

 One of the important requirements for screw-type bottle caps is the opening torque of the bottle cap, which is the force until the bottle is opened by rotating the bottle to drink a drink. It is impossible to open a drink, and if the opening torque is too weak, there is a problem of storing the contents. Therefore, the opening torque of the bottle cap is generally defined as a proper force of 7-18 lb-inch (in). Opening torque is the main factor due to the friction force between the bottle opening of the bottle, such as glass bottles or polyethylene terephthalate, and the bottle cap.To solve this problem, US Patent No. 4710409 adds a lubricant of oil type to reduce the friction force of the bottle cap. The technique of reducing the amount of is disclosed, and also US Pat.

However, the above-described conventional technique adds a low molecular weight oil and a lubricant such as fatty acid amide which are incompatible with resins such as polyethylene and polypropylene, so that the low molecular material is leached onto the bottle cap surface to cause a change in the taste of the contents. Recently, its use has been suppressed, and especially in the case of juices and ionic beverages, a high temperature sterilization process is required at 90 ° C., so that a low molecular weight lubricant having a low melting temperature of 70 to 80 ° C. is dissolved in the contents. .

 An object of the present invention is to solve the above problems, by melting and kneading polyethylene grafted on the alkyl silicone polyethylene backbone with high-density polyethylene mixed with high-density polyethylene to show the appropriate bottle opening torque by the friction coefficient reduction and changes in the taste of the contents To provide a high-density polyethylene resin composition for the bottle cap does not cause.

Polyethylene resin composition of the present invention is characterized in that the polyethylene made by grafting the alkyl silicon oxide compound to 100 parts by weight of the high-density polyethylene is mixed by 5 to 20 parts by weight.

In the polyethylene resin composition of the present invention, a copolymer of an ethylene homopolymer and one or more monomers is used as the high density polyethylene. As monomers that can be used, linear or branched alpha olefins containing 4 to 6 carbon atoms can be used, for example butene-1, hexene-1, 4-methylpentene-1. In particular, in the polyethylene resin composition of the present invention, the high density polyethylene has a melt index of 0.1 g / 10 min to 10 g / 10 min when measured at 190 ° C. under a 2.16 kg load according to ASTM D1238, and 23 ° C. according to ASTM D1505. High density polyethylenes with a density of at least 0.950 g / cm ³ are suitable.

Meanwhile, as the polyethylene grafted with the alkylsilicon oxide compound, an ethylene-vinyltriethoxysilane copolymer and a silicone oil having a silane end group are reacted and extruded using a dibutyltindilaurate catalyst to produce an alkylsilicon oxide on the polyethylene main chain. Grafted compounds can be used. For example, Ruboten from OPTATECH can be used. The grafting rate of the alkylsilicon oxide compound is suitably 1 to 10% by weight based on the weight of the silicon molecules. If it is less than 1% by weight of silicon, it is difficult to exhibit the effect, and if it exceeds 10% by weight, there is a problem that economic efficiency is lowered.

It is well known that silicone has a property of reducing the friction coefficient of the surface as an external lubricant, and the polyethylene grafted with the alkylsilicon oxide compound of the present invention has a weight average molecular weight of 200,000 or more, 1 to 10 weight per 100 parts by weight of polyethylene. Parts with a silicon content, and the amount thereof is preferably 5 to 20 parts by weight, more preferably 7 to 12 parts by weight, per 100 parts by weight of high density polyethylene. At this time, less than 5 parts by weight has little effect of reducing the coefficient of friction, and if it exceeds 20 parts by weight, there is a disadvantage in that the sealing property due to creep deterioration is lowered when the bottle cap for carbonated beverage is applied.

In the polyethylene resin composition of the present invention, in addition to polyethylene to which the alkylsilicon oxide compound is grafted, additives such as acid and antioxidants may be contained. Each content of these additives in the composition is generally 1 part by weight or less, preferably 0.5 parts by weight or less. In addition, the composition according to the present invention may contain a pigment for indicating the color of the bottle cap. Generally, the pigment content does not exceed 2 parts by weight of the composition.

One preferred method for producing a composition according to the present invention is 100 parts by weight of a high density polyethylene using a general twin screw extruder, 5 to 20 parts by weight of polyethylene grafted to 1 to 10% by weight of an alkylsilicon oxide compound on the basis of the silicone molecular weight, acid-resistant 0.01 to 0.5 parts by weight of the antioxidant, 0.01 to 0.5 parts by weight of the antioxidant is uniformly dispersed using a Henschel mixer, and then put into the main supply of the extruder and melt-extruded at a temperature of 150 to 220 ℃ mixed. The composition is preferably in the form of extruded pellets.

The resin composition prepared as described above can be used both in the general bottle cap manufacturing molding method such as compression molding and injection molding.

In addition, the present invention relates to a bottle cap molded of the resin composition according to the present invention, the bottle cap prepared by the composition exhibits a suitable bottle opening torque with a low coefficient of friction characteristics, at the same time there is no leaching into the beverage of taste You can keep your drink unchanged.

Hereinafter, the present invention will be described in detail through examples. However, these examples are for illustrative purposes only, and the present invention is not limited thereto.

Example

Preparation of the bottle cap molding according to an embodiment of the present invention and the evaluation method of the bottle cap prepared therefrom are as follows.

The bottle caps were manufactured using an injection machine having 48 cavities with a 28mm standard, and were molded under the injection conditions of injection temperature of 250 ° C, injection pressure of 175 bar, injection speed of 160mm / sec, injection time of 2 seconds, and injection holding pressure of 45 bar. .

Friction Coefficient: An injection specimen having a thickness of 2 mm was prepared and measured by static friction coefficient according to ASTM D3428.

Opening torque of the bottle cap: After annealing the molded bottle cap at room temperature for 48 hours, 350 ml of polyethylene terephthalate and glass substrate containers are filled with carbonated beverages with 4.0 vol% carbonated gas and the bottle cap is closed with 18 lb-in of force. After locking, the torque was measured over time up to 12 weeks at 3 ° C using a torque meter.

Carbonation Retention Test: Fill a 350 ml polyethylene terephthalate bottle with 4.0 vol% carbonated gas, lock the bottle with 18 lb-in force, and place it in a 42 ° C oven for 12 weeks. The carbon dioxide concentration up to was measured. The carbon dioxide concentration was measured by measuring the carbon dioxide pressure in the bottle and converting it to the carbon dioxide concentration.

Heat Cycle Test: After preparing the specimens in the same manner as the carbonation retention test, repeat the oven's temperature conditions three times in a cycle of 6 hours at 60 ℃ and 18 hours at 32 ℃ to determine whether the bottle cap is deformed. Evaluated.

Taste test of beverages: 500 g of pellets were placed in 500 ml flasks, filled with bottled water and left for 48 hours in an oven at 60 ° C. for 48 hours, followed by natural cooling for 48 hours. In order to give objectivity to the evaluation of taste, five experimenters who were experienced in the test were composed and evaluated separately.

Example 1

A melt index of 0.5g / 10 minutes, high-density polyethylene (HDPE1) powder is an alkyl silicon oxide compound to 100 parts by weight of the grafted polyethylene (RLF-0803 having a silicon content of 3% by weight has a density 0.962g / cm ^3, Optatech Co.) 7 parts by weight, calcium stearate 0.1 part by weight, pentaerythritol tetrakis (3- (3,5-di-tet-butyl-4-hydroxyphenyl) propionate) 0.05 part by weight, tri (2,4-di-tet-butylphenyl) phosphite 0.1 parts by weight of the total mixture to 50kg mixed with a Henschel mixer, and then extruded at a processing temperature of 220 ℃ using a twin screw extruder into pellets Prepared.

After the injection sheet and the bottle cap were manufactured with the composition, the friction characteristics and the performance of the bottle cap were measured. As a result, the friction coefficient was 0.22, the opening torque after 12 weeks was 12-15 lb-in, and the carbonation retention was 3.90% by volume. In the heat cycle, there was no deformation of the bottle cap and no change in taste.

Example 2

Polyethylene (RLF-0806) having a silicon content of 6 wt% by grafting an alkylsilicon oxide compound to 100 parts by weight of a high density polyethylene (HDPE2) powder having a melt index of 2.2 g / 10 min and a density of 0.955 g / cm ³ Optatech Co.) 7 parts by weight, calcium stearate 0.1 part by weight, pentaerythritol tetrakis (3- (3,5-di-tet-butyl-4-hydroxyphenyl) propionate) 0.05 part by weight, tri As a result of evaluating the physical properties after molding under the same conditions as in Example 1 at a ratio of 0.1 part by weight of (2,4-di-tet-butylphenyl) phosphite, the friction coefficient was 0.26, and the opening torque after 12 weeks was 13 to 15.5 lbs. -in, the carbonation retention was 3.80% by volume, and there was no deformation of the bottle cap in the heat cycle and no change in taste.

Example 3

As a result of evaluating after molding under the same conditions, 12 parts by weight of polyethylene (RLF-0803, OPTATECH) having a silicon content of 3% by weight is grafted with an alkylsilicon oxide compound in the resin composition of Example 1, the coefficient of friction is 0.15 After 12 weeks, the opening torque was 10.5-12 ib-in and the carbonation retention was 3.80% by volume. There was no deformation of the bottle cap and no change of taste in the heat cycle.

Comparative Example 1

0.1 part by weight of calcium stearate, 100 parts by weight of high density polyethylene (HDPE3) powder having a melt index of 0.55 g / 10 minutes and a density of 0.958 g / cm ^3, and pentaerythritol tetrakis (3- (3,5-di) -Tet-butyl-4-hydroxyphenyl) propionate) 0.05 parts by weight and tri (2,4-di-tet-butylphenyl) phosphite in a ratio of 50 parts by weight of the mixture to a Henschel mixer After mixing, the resultant was extruded at a processing temperature of 220 ° C. using a twin screw extruder to prepare pellets.

After the injection sheet and the bottle cap were prepared from the composition, the friction characteristics and the performance of the bottle cap were measured. As a result, the friction coefficient was 0.45, the opening torque after 19 weeks was 19 to 23 lb-in, and the carnation retention was 3.90% by volume. In the heat cycle, there was no deformation of the bottle cap and no change in taste.

Comparative Example 2

To the same resin composition as Comparative Example 1, 0.3 parts by weight of low molecular weight erucamide was added to make the whole mixture 50 kg, mixed with a Henschel mixer, and then extruded at a processing temperature of 220 ° C. using a twin screw extruder. To prepare pellets.

After the injection sheet and the bottle cap were manufactured with the composition, the friction characteristics and the performance of the bottle cap were measured. As a result, the friction coefficient was 0.25, and the opening torque after 12 weeks was 13.5-15.5 lb-in, and the carbonation retention was 3.90% by volume. There was no deformation of the bottle cap in the heat cycle, but a change in the taste of the contents occurred.

The result of the said Example is shown in Table 1, and the result of the comparative example is shown in Table 2.

Table 1

Example 1 Example 2 Example 3 Resin composition (parts by weight) HDPE 1 100 0 100 HDPE 2 0 100 0 RLF-0803 (1) 7 0 12 RLF-0806 (2) 0 7 0 Phenolic Antioxidant (3) 0.05 0.05 0.05 Phosphite Antioxidants (4) 0.1 0.1 0.1 Calcium stearate 0.1 0.1 0.1 Resin properties Melt Index (190 ℃, 2.16kg) 0.38 1.9 0.41 density 0.958 0.954 0.954 Coefficient of friction Static friction coefficient 0.22 0.26 0.15 Bottle cap performance After 1 week of opening torque (PET / GLASS) After 4 weeks (lb / in) After 8 weeks 12 weeks 15.5 / 17.0 14.5 / 16.5 14.5 / 15.5 12.0 / 15.0 15.5 / 16.0 15.0 / 15.5 13.0 / 16.0 13.0 / 15.5 14.0 / 15.0 12.0 / 13.5 12.5 / 13.5 10.5 / 12.0 Carbonate Retention (After 12 weeks, Volume%) 3.90 3.80 3.80 Heat cycle test clear clear clear Taste Test No change No change No change

(week)

(1) RLF-0803: Polyethylene (OPTATECH Co., Ltd.) having a silicon content of 3% by weight grafted with an alkylsilicon oxide compound

(2) RLF-0806: Polyethylene (OPTATECH Co., Ltd.) having a silicon content of 6% by weight by grafting an alkylsilicon oxide compound

(3) PHENOL type antioxidant: pentaerythritol tetrakis (3- (3,5-di-tet-butyl-4-hydroxyphenyl) propionate)

(4) PHOSPHITE type antioxidant: tri (2,4-di-tet-butylphenyl) phosphite

TABLE 2

Comparative Example 1 Comparative Example 2 Resin composition (parts by weight) HDPE 3 100 100 Phenolic Antioxidant (1) 0.05 0.05 Phosphite Antioxidants (2) 0.1 0.1 Calcium stearate 0.1 0.1 Eruick Amide 0 0.3 Resin properties Melt Index (190 ℃, 2.16kg) 0.38 0.38 density 0.958 0.958 Coefficient of friction Static friction coefficient 0.45 0.25 Bottle cap performance After 1 week of opening torque (PET / GLASS) After 4 weeks (lb / in) After 8 weeks 12 weeks 22.0 / 26.5 21.5 / 24.5 21.5 / 23.5 19.0 / 23.0 15.5 / 16.0 15.0 / 15.5 14.0 / 15.5 13.5 / 15.5 Carbonate Retention (After 12 weeks, Volume%) 3.90 3.90 Heat cycle test clear clear Taste Test No change Change

(week)

(1) PHENOL-based antioxidant: pentaerythritol tetrakis (3- (3,5-di-tet-butyl-4-hydroxyphenyl) propionate)

(2) PHOSPHITE-based antioxidant: tri (2,4-di-tet-butylphenyl) phosphite

As can be seen from the results of Table 1 and Table 2, the bottle cap prepared from the resin composition containing polyethylene having a silicon content of 1 to 10% by weight is grafted with an alkylsilicon oxide compound to add the lubricant of Comparative Example 1 Compared with the composition that did not have a significantly lower coefficient of friction and the appropriate opening torque was maintained, it was confirmed that does not cause a change in the taste of the contents shown in Comparative Example 2 using a conventional conventional low molecular weight lubricant.

 As described above, the bottle cap molded by using the polyethylene resin composition prepared according to the present invention showed a low coefficient of friction and a proper opening torque, and compared to the contents of the bottle lid when using a conventionally used low molecular lubricant. It was confirmed that the stability of the taste is excellent.

Claims (5)

A polyethylene resin composition for plastic bottle caps, comprising 100 parts by weight of high density polyethylene and 5 to 20 parts by weight of polyethylene grafted with an alkylsilicon oxide compound. The plastic according to claim 1, wherein the high density polyethylene has a melt index in the range of 0.1 to 10 g / 10 minutes and a density of at least 0.950 g / cm ³ when measured at 190 ° C with a load of 2.16 kg according to ASTM D1238. Polyethylene resin composition for bottle caps. The plastic bottle cap according to claim 1, wherein the polyethylene grafted with an alkylsilicon oxide compound has a molecular weight of 200,000 or more and an alkylsilicon oxide is grafted in an amount of 1 to 10% by weight based on the weight of the silicon molecules. Polyethylene resin composition for use. The polyethylene resin composition for plastic bottle caps according to claim 1, further comprising 0.01 to 0.5 parts by weight of an acid resistant agent and 0.01 to 0.5 parts by weight of an antioxidant. Bottle cap made of a polyethylene resin composition according to any one of claims 1 to 4.